what we know about Time

[Spyman]

You wrote: (bolded mine)

But the thing is that there is another you in the past waving at you in the future and it is in theory possible for you to observe it.

 

Contradicted by this statement:

 

When I look in a mirror I belive I see myself in the past, the real me, not another Spyman that is not me or something else.

Yes sure, but that was not the only thing I wrote, was it? You are cherry picking statements and ignoring the context.

 

 

It is Michel's image travelling at c.

Yes, of course it is an image travelling at c, you are avoiding the question and trying to wriggle your way out of it.

 

 

But I will retain your statement "The triangle is her light cone so she can't see the red dot (one second behind her in the -t direction)." This only was worth the thread. That is because 2 years now I struggle maintaining that the interior part of the PLC is not observable. It was then dumped into the Forum waste basket.

I thought I proved in my post #141 that the interior is observable and you agreed, but never mind carry on...

Edited March 29, 2012 by Spyman

[michel123456]

I thought I proved in my post #141 that the interior is observable and you agreed, but never mind carry on...

 

Lets do it. Put today 29th of March 2012 a mirror on Moon's surface. Is it possible to see in this mirror anything happening before 29th of March? I don't think so. The only thing that you will do is provide an instrument for the future generations in order to have a look at their own image in their past as it was 3 sec. ago. That will not prove that in the future there will be 2 Earths, one in the present and one with 3 sec. of delay.

[Iggy]

Marion is at the origin.

That's right, I previously said Marion was at x=0, y=0, z=0, t=12:00:10

 

Here then:

 

 

But I will retain your statement "The triangle is her light cone so she can't see the red dot (one second behind her in the -t direction)." This only was worth the thread. That is because 2 years now I struggle maintaining that the interior part of the PLC is not observable. It was then dumped into the Forum waste basket.

Again, I'm working off of your premise. I'm using your interpretation of spacetime.

 

So far you have not been able to tell me what the red dot is, but you are sure it is not Marion.

 

Marion's friend is one light second away. What does he see when he looks toward Marion?

 

 

1) does he see the red dot?

 

2) how does he identify it?

[Spyman]

Lets do it. Put today 29th of March 2012 a mirror on Moon's surface. Is it possible to see in this mirror anything happening before 29th of March? I don't think so. The only thing that you will do is provide an instrument for the future generations in order to have a look at their own image in their past as it was 3 sec. ago.

Whether you like it or not, that is enough to disprove your claim that the inside of an observer's past light cone is not observable.

 

 

That will not prove that in the future there will be 2 Earths, one in the present and one with 3 sec. of delay.

I have not tried to prove that in the future there will be 2 Earths, one in the present and one with 3 sec. of delay.

[michel123456]

That's right, I previously said Marion was at x=0, y=0, z=0, t=12:00:10

 

Here then:

 

 

 

Again, I'm working off of your premise. I'm using your interpretation of spacetime.

 

So far you have not been able to tell me what the red dot is, but you are sure it is not Marion.

 

Marion's friend is one light second away. What does he see when he looks toward Marion?

 

 

1) does he see the red dot?

 

2) how does he identify it?

Paul is not observable from Marion In Black, And Marion In Black is not observable from Paul. What Paul observes is Marion in red, for him, ONLY Marion in Red is observable, Marion in black is not part of his (observable) universe. If you want to discuss what Paul observes, you have to put Paul at the origin.

 

So

1) yes Paul observes Marion in red, but neither Paul nor Marion in red are part of Marion In Black's (observable) universe. It is like saying that a planet 250 million LY away from us "today" observes dinosaurs on Earth. Neither the planet is observable to us, neither the dinosaurs. And IMHO the reason for that is that both the planet and the Earth have translated in Time.

 

2) He identifies Marion, the object, with mass. For him Marion in Black doesn't exist (yet). As I stated before, there is only one King in the chess game. There is only one Marion, you have to choose.

 

Whether you like it or not, that is enough to disprove your claim that the inside of an observer's past light cone is not observable.

 

 

 

I have not tried to prove that in the future there will be 2 Earths, one in the present and one with 3 sec. of delay.

Edited March 30, 2012 by michel123456

[Iggy]

What Paul observes is Marion in red, for him, ONLY Marion in Red is observable

I thought the red dot wasn't Marion. Now you say it is. Could you clarify?

 

If you want to discuss what Paul observes, you have to put Paul at the origin.

I've never heard such a thing. What do you mean by "origin"?

[michel123456]

I thought the red dot wasn't Marion. Now you say it is. Could you clarify?

 

Observation is relative. If Paul observes Marion In Red (MIR), he cannot observes Marion In Black (MIB). For him, in all his universe, Marion in Black does not exist. If he wants to measure Marion, the object Marion is Marion In Red, Mir has mass, MIR is measurable. MIR is the King on the chessboard for Paul. And for Paul, MIR is his companion.

On the other hand MIB is unobservable to Paul. If MIB was a square instead of a dot, Paul would have no clue.

When MIR will reach the coordinates of MIB, MIB will have gone further in time, and Paul also. The diagonal that links Paul with MIR is unescapable, Paul & MIR are tied together. Wathever is out of the diagonal is only a guess.

 

I've never heard such a thing. What do you mean by "origin"?

You understood clearly in post #153

Edited March 30, 2012 by michel123456

[Iggy]

Observation is relative. If Paul observes Marion In Red (MIR), he cannot observes Marion In Black (MIB).

I understand that Paul can't see the black dot. I also understand that Marion can't directly see (by line of sight) the red dot. Those things are not what I'm asking.

 

I'm trying to determine what the red dot in your model is. You keep saying that it is Marion ("Marion in red"), but earlier you said that the one thing the red dot couldn't be is Marion.

 

I'm not asking how many dots at x=0 Paul can observe at 12:00:10... or how many dots any observer can observe at any spatial location at any time. I'm just trying to figure out, according to your model of spacetime, how do we label the red dot?

 

 

From your interpretation and statements: we know Paul can identify it because it is on his past light cone, we know it isn't Marion because she can't be more than one dot, and we know it is an object because objects are dots in your model.

 

If your model of spacetime works there should be a reasonable answer. How do we label the red dot?

 

 

You understood clearly in post #153

In that post I said Marion is at 0,0,0,12:00:10. Paul is one light second left of Marion. He is at -1,0,0,12:00:10. That is where he is in the real world and that is where he is in the diagram. I don't know what you mean by "origin" and I don't know why you are saying to put him there.

Edited March 31, 2012 by Iggy

[michel123456]

(...)

From your interpretation and statements: we know Paul can identify it because it is on his past light cone, we know it isn't Marion because she can't be more than one dot, and we know it is an object because objects are dots in your model.

 

If your model of spacetime works there should be a reasonable answer. How do we label the red dot?

 

 

 

In that post I said Marion is at 0,0,0,12:00:10. Paul is one light second left of Marion. He is at -1,0,0,12:00:10. That is where he is in the real world and that is where he is in the diagram. I don't know what you mean by "origin" and I don't know why you are saying to put him there.

Bolded mine.

You are mixing 2 POV, it is like mixing 2 FOR: you can't do that and expecting to extract a safe result.

 

If you are examining Marion, then Marion is at the origin, that is your diagram.

If you want to examine what Paul's observations are, you have to make a entirely new diagram and label Paul in the place & time of Marion. You cannot superpose the 2 diagrams and declare that "we know it isn't Marion because she can't be more than one dot", it is not a safe conclusion, it is a bad mixing.

 

 

Labelling is simple: each point of the diagram must be labeled with coordinates. Marion In Black is (0,0,0,0), Marion In Red is (0,0,0,-1). It is the same and one Marion at different spacetime coordinates.

[Iggy]

I see a number of your comments trying to explain why your diagram and your spacetime interpretation isn't working the way you've previously explained, but I also know the things you're saying are false and I feel the need to correct them.

 

You are mixing 2 POV, it is like mixing 2 FOR: you can't do that and expecting to extract a safe result.

Both Marion and Paul are in the same frame of reference. Both exist at the same time. Both are property placed on the same diagram.

 

If Paul identifies the red dot as Marion then everyone in that diagram needs to agree that the dot is Marion. This is the way that every spacetime diagram has ever been made, and you have given no reason for this one to be different.

 

If Paul determines that Marion was at 0,0,0,12:00:09 because he sees her there, it is impossible for Marion not to have been there. The red dot carries the same label regardless of who determines what it is.

 

If your model of spacetime is different (only one observer's observations in any given diagram count), then the diagram has no usefulness.

 

Spacetime diagrams also show multiple frames of reference and allow one to relate observations made in one frame to observations made in another although that isn't necessary or relevant for this example. For example, Marion's proper time between 12:00:09 and 12:00:10 can be calculatee by any observer in a diagram and they would all get the same correct answer.

 

I therefore wonder if you are dissembling to try and cover the problem with your spacetime interpretation.

 

 

If you are examining Marion, then Marion is at the origin, that is your diagram.

If you want to examine what Paul's observations are, you have to make a entirely new diagram and label Paul in the place & time of Marion.

The x axis means "light-seconds from earth". Marion is at zero light-seconds from earth because she is on earth. Paul is at -1 light-seconds on the diagram because he is 1 light-second to Earth's left. I can't re-label Paul putting him somewhere that he doesn't exist. He is at -1,0,0,12:00:10.

 

I can only move him on the diagram if I move him in real life

 

You cannot superpose the 2 diagrams and declare that "we know it isn't Marion because she can't be more than one dot", it is not a safe conclusion, it is a bad mixing.

Putting 2 observers on a diagram is not bad mixing. It isn't mixing at all. Paul is at -1,0,0,12:00:10 . That is his space-time position. That is where he goes on the space-time diagram.

 

He is an observer. He has a past light cone. And, he makes observations. If you have some problem with what he sees then that is a problem with your interpretation of spacetime. You can't deny that he belongs in his spacetime coordinates or that he does what he would do in real life -- make observations.

 

In real life he would also compare his obsrvations with Marion, so we can't deny him that opportunity.

 

 

Labelling is simple: each point of the diagram must be labeled with coordinates. Marion In Black is (0,0,0,0), Marion In Red is (0,0,0,-1). It is the same and one Marion at different spacetime coordinates.

When I previously said that multiple dots represent the same object I was met with a lot of resistance. I said, in fact, that a multitude of dots making up the world-line are one and the same objects.

 

Do you agree now? You're saying that two of the dots are the same object. Can I assume that more are (if there were more observers for example) as well?

 

Please keep in mind after all this -- I'm working off your assumption that objects are dots that move through spacetime. I'm accepting your premise for the purpose of discussion.

Edited March 31, 2012 by Iggy

[michel123456]

When I previously said that multiple dots represent the same object I was met with a lot of resistance. I said, in fact, that a multitude of dots making up the world-line are one and the same objects.

 

Do you agree now? You're saying that two of the dots are the same object. Can I assume that more are (if there were more observers for example) as well?

 

Please keep in mind after all this -- I'm working off your assumption that objects are dots that move through spacetime. I'm accepting your premise for the purpose of discussion.

IIRC you said that an object persist in time, I said that an object moves in time. There is a difference between our interpretations.

 

Both Marion and Paul are in the same frame of reference. Both exist at the same time. Both are property placed on the same diagram.

 

If Paul identifies the red dot as Marion then everyone in that diagram needs to agree that the dot is Marion. This is the way that every spacetime diagram has ever been made, and you have given no reason for this one to be different.

 

For Marion, Paul is constantly in her past.

For Paul, Marion is constantly in his past.

There is no reason for putting one or the other in a priviligiated situation, so there is a kind of incompability.

If you superpose the 2 POV, you will obtain multiple Marions and Pauls, which is not what is observed at no time.

 

When you superpose the 2 POV, you obtain a diagram in which Paul is in the past of Marion AND Marion is in the past of Paul. So you get 2 Marions & Pauls: it is wrong. The diagram may give the correct numerical result for the relative coordinates of Marion & Paul, but they didn't duplicate in time.

 

-----------------------------------

trying to explain my point:

if (IF) Speed Of Light was infinite, Marion & Paul would be in their mutual present : instead of the SOL line at 45 degrees down, there would be a horizontal link between Paul & Marion.

But SOL is not infinite, so there is a diagonal link between Paul & Marion. But beside the fact that the link is diagonal instead of horizontal, is that an enough good reason to postulate the existence of multiple Marions in your diagram?

Edited March 31, 2012 by michel123456

[Iggy]

 

 

But beside the fact that the link is diagonal instead of horizontal, is that an enough good reason to postulate the existence of multiple Marions in your diagram?

That isn't my decision. This is your model of spacetime.

 

 

For Marion, Paul is constantly in her past.

For Paul, Marion is constantly in his past.

There is no reason for putting one or the other in a priviligiated situation, so there is a kind of incompability.

If you superpose the 2 POV, you will obtain multiple Marions and Pauls, which is not what is observed at no time.

That certainly is an incompatibility. If Marion is the red dot according to one person and the black dot according to another person while both people are correct, and she can only be one dot, then your model is inconsistent with itself.

 

It gives two answers, both of which are correct, only one of which can be correct. That means it is internally inconsistent, and since we are in the physics forum it is enough to say that the inconsistency falsifies the model.

 

Marion can't be both:

 

1. only one dot
   
2. the black and red dot depending on perspective
   

 

Do you have any suggestions for fixing the problem?

 

When you superpose the 2 POV, you obtain a diagram in which Paul is in the past of Marion AND Marion is in the past of Paul. So you get 2 Marions & Pauls: it is wrong. The diagram may give the correct numerical result for the relative coordinates of Marion & Paul, but they didn't duplicate in time.

It sounds like you are suggesting that every diagram have only one person on it -- suggesting that I remove Paul from the diagram. That way no two observers will ever be 'superimposed' onto the same diagram.

 

In other words, if your model works when only one observer is diagrammed, it sounds like your solution is to only ever diagram one observer. If the universe only had one observer then this would be a reasonable solution, but it doesn't and it clearly isn't.

 

Do you have any solution to propose?

Edited April 1, 2012 by Iggy

[michel123456]

 

 

 

That isn't my decision. This is your model of spacetime.

 

 

 

That certainly is an incompatibility. If Marion is the red dot according to one person and the black dot according to another person while both people are correct, and she can only be one dot, then your model is inconsistent with itself.

 

It gives two answers, both of which are correct, only one of which can be correct. That means it is internally inconsistent, and since we are in the physics forum it is enough to say that the inconsistency falsifies the model.

I don't think so. With such a syllogism you may falsify the whole theory of relativity.

 

Marion can't be both:

 

1. only one dot
   
2. the black and red dot depending on perspective
   

Yes she can. In space it is called motion: Marion can be at 2 different coordinates in space, I hope you agree on this. What i say is simply that the same and only one Marion can be at 2 coordinates of spacetime because she "moved" from one coordinate to the other. The 2 points on the diagram cannot be interpretated as "2 marions". If you choose Marion In Black as observer, then Marion In Red is gone. If you choose Paul as observer, then Marion in Red is there and Marion in Black is not. You cannot choose al POV "at the same time" and get a safe result. The diagram gives a wrong impression because it is a mix of different observers.

Do you have any suggestions for fixing the problem?

 

 

It sounds like you are suggesting that every diagram have only one person on it -- suggesting that I remove Paul from the diagram. That way no two observers will ever be 'superimposed' onto the same diagram.

 

In other words, if your model works when only one observer is diagrammed, it sounds like your solution is to only ever diagram one observer.

Each observer has its own diagram. I don't understand why it should be surprising.

 

If the universe only had one observer then this would be a reasonable solution, but it doesn't and it clearly isn't.

This is a strawman. i never argued that there is only one observer nor that there exist an ultimate "truth" connected to a single observer. Quite the contrary.

Do you have any solution to propose?

IMHO the problem is not in my "model" (it is not a model, it is an interpretation). You still haven't answer clearly to the question "where is mass" in your interpretation of objects that "persist" in time.

 

(Pause)---------------------------------------------

---------------------------------------------

---------------------------------------------(end of pause)

 

 

Diagram A (see below) is an hypothetical figure where Speed Of Light is infinite. Observation between Marion & Paul is instantanate. Their observations are reversed and mutual, there is no delay. There are 2 points called "Marion" and 2 points called "Paul", but there are no 2 Marions nor 2 Pauls. The diagram shows the translation of Marion & Paul in time. To me it is obvious like 1+1=2.(To you I see it is not)

.

 

 

Diagram B is what really happens, SOL is not infinite, there is a delay between observations. But there is no fundamental change with diagram A as far as the nature of Marion & Paul is concerned. Marion & Paul do not "persist" in time any more than in diagram A.

 

Marion & Paul are not extruded in time due to the angle of SOL. The following W diagram is not what happens.

Edited April 1, 2012 by michel123456

[Iggy]

I don't think so. With such a syllogism you may falsify the whole theory of relativity.

You can put as many observers as you want in space-time using relativity. It is not constrained by inconsistencies the way yours is.

 

Yes she can. In space it is called motion: Marion can be at 2 different coordinates in space, I hope you agree on this. What i say is simply that the same and only one Marion can be at 2 coordinates of spacetime because she "moved" from one coordinate to the other.

I understand your belief that Marion moved from 12:00:09 to 12:00:10.

 

It means that if Marion is at 12:00:10 (if she is the black dot) then she cannot be at 12:00:09 (she cannot be the red dot)

 

 

But, at 12:00:10, by your interpretation, according to Paul the red dot is Marion. This means that Marion is two different dots at the same time. You say that she can't be two different dots at the same time, and you say that she is two different dots at the same time depending on perspective. That is internally inconsistent... a serious problem that you haven't answered.

 

 

The 2 points on the diagram cannot be interpretated as "2 marions". If you choose Marion In Black as observer, then Marion In Red is gone. If you choose Paul as observer, then Marion in Red is there and Marion in Black is not. You cannot choose al POV "at the same time" and get a safe result. The diagram gives a wrong impression because it is a mix of different observers.

Two different people can observe the world at the same time. This is a fact of the real world and space-time diagrams need to reflect that fact. There is nothing unsafe about simultaneous observations in a typical diagram and there is no reason for it to be unsafe. No space-time diagram has ever had a problem with comparing the observations of multiple observers.

 

This appears to be something that you have made up (invented) because of the specific problem your worldview has, and you haven't done anything to support such a strange notion. If you didn't model objects in space-time in a manner inconsistent with reality you wouldn't have this problem.

 

Each observer has its own diagram. I don't understand why it should be surprising.

What is surprising is that you refuse to complete or consider both Paul and Marion's observations in the same diagram. This is surprising because,

 

First, because that has never been a condition of space-time diagrams of any type. Diagrams have always included multiple observers.

 

Second, because more than one observer exists between -2 < x < 1. They are both located in the area diagrammed so they both belong on the diagram.

 

The problem with your interpretation is more than just diagramming. Regardless of the diagram, you say that Marion moves from 00:09 s to 00:10 s and that she can't exist at both times 'simultaneously'. At 00:10 s Marion is at 00:10 s according to Marion and 00:09 s according to Paul. Both observers, you say, are correct. At 00:10 s Marion exists at two locations in space-time. This fundamentally disagrees with your statements.

 

Your 'solution' is to say that Marion cannot compare observations with Paul. But, in reality people compare observations all the time. One person's truth needs to agree with the truth of another.

 

If Marion is a single dot on a spacetime diagram then either she is the red dot or the black dot.

 

You still haven't answer clearly to the question "where is mass" in your interpretation of objects that "persist" in time.

Yes, I have.

 

According to the normal scientific interpretation and method, where is the object? A hint: the object does not exist at only one specific point along a world-line.

 

Mass is a property of objects so the answer to "where is mass" is the same as the answer above.

 

I have a feeling you will only accept an answer that gives the location of mass somewhere (some single specific location) along the world-line of the object because you presume that mass should multiply beyond its correct value if it exists at more than one time.

 

I wish you understood that your presumption concerning mass comes from trying to fit the typical understanding of space-time (in which objects and mass are not dots moving on the manifold) into your understanding of space-time where they are.

 

For the typical scientific functionality and interpretation of space time to make sense it would require a completely different view and understanding than the one you have... you don't appear to be able to think outside the box your views have put you in.

Edited April 1, 2012 by Iggy

[michel123456]

(...)

I have edited my post.

 

You can put as many observers as you want in space-time using relativity. It is not constrained by inconsistencies the way yours is.

But their observation will be different. By definition.

 

 

 

I understand your belief that Marion moved from 12:00:09 to 12:00:10.

That's good.

 

It means that if Marion is at 12:00:10 (if she is the black dot) then she cannot be at 12:00:09 (she cannot be the red dot)

Yes.

 

But, at 12:00:10, by your interpretation, according to Paul the red dot is Marion. This means that Marion is two different dots at the same time. You say that she can't be two different dots at the same time, and you say that she is two different dots at the same time depending on perspective. That is internally inconsistent... a serious problem that you haven't answered.

??? Did I say that? If I did I apologize. It seems we have a diametrical opposite view of things.

 

 

Two different people can observe the world at the same time. This is a fact of the real world and space-time diagrams need to reflect that fact. There is nothing unsafe about simultaneous observations in a typical diagram and there is no reason for it to be unsafe. No space-time diagram has ever had a problem with comparing the observations of multiple observers.

I didn't argue that. What i argue is about the conclusion we drive when looking at the diagram and putting a bunch of Marions because there are a bunch of observers.

 

This appears to be something that you have made up, or invented, because of the specific problem your worldview has, and you haven't done anything to support such a strange notion.

The strange notion IMHO is to believe that objects (and thus mass) are elungated in time.

 

Only your model of space-time has trouble with multiple observers because it diagrams objects in a manner inconsistent with reality.

I didn't know I was so unique.

 

 

First, because that has never been a condition of space-time diagrams. Diagrams have always included multiple observers.

 

Second, because more than one observer exists between -2 < x < 1. They are both located in the area diagrammed so they both belong on the diagram.

I didn't argue that. I argued against the conclusion, see above.

 

The problem with your interpretation is more than just diagramming. Regardless of the diagram, you say that Marion moves from 00:09 s to 00:10 s and that she can't exist at both times 'simultaneously'. At 00:10 s Marion is at 00:10 s according to Marion and 00:09 s according to Paul. Both observers, you say, are correct. At 00:10 s Marion exists at two locations in space-time. This fundamentally disagrees with your statements.

There is a full misunderstanding: yes both observers are correct, and they disagree on observations, by definition. When you superpose 2 different observations in the same diagram, what do you expect?

 

Your 'solution' is to say that Marion cannot compare observations with Paul. But, in reality people compare observations all the time. One person's truth needs to agree with the truth of another.

Nobody argued that Marion didn't exist in the past. Nobody argued against observation of the one or the other, both are correct.

 

If Marion is a single dot on a spacetime diagram then either she is the red dot or the black dot.

Yes, you have to choose a configuration. You cannot take all configurations superposed.

 

 

Yes, I have. I've given multiple answers that answer in multiple different ways. But, you haven't been able to fit the answer I gave into your "objects are dots that move in space-time" worldview. The answer, therefore, doesn't make sense to you.

 

What you are really asking is, "where along the world-line is the mass because if it repeats along the world-line it will multiply beyond its correct value."

 

That question is presupposes the equivalence of dots on a spacetime diagram and objects. By definition that is untrue and it is based on a misunderstanding of space-time. It is no different from asking "where in time is Japan?". I can't answer that question with a year. But, my unwillingness to give a year for the existence of Japan or to give a year when Japan has the property of mass doesn't mean I haven't answered the question. It just means that you are basing the question on a misunderstanding.

I agree about the misunderstanding.

If I understand clearly, you say that it is incorrect to make a Mass-Space_Time diagram because it is based on a false assumption. Is that it?

Edited April 1, 2012 by michel123456

[Iggy]

I have edited my post.

Same here.

 

Let's re-read and I'll get some sleep and we'll get back together subsequent.

[michel123456]

This is what I understand concerning 2 objects AT REST as they travel in time. The small yellow dot is a ray of light.

 

If you could rotate the diagram 90 degrees in such a way to see the thin side of the sheet of paper, you would see a ray of light coming from the red dot (which is AT REST) to the black dot (at rest), and the labelling of time given by a clock.

Edited April 1, 2012 by michel123456

[Spyman]

This is what I understand concerning 2 objects AT REST as they travel in time. The small yellow dot is a ray of light.

What happened with:

 

For me the surface of the Past Light Cone is occupied by our companions traveling with us in time.

This last diagram have the companion comoving in the present and not at the surface of the Past Light Cone.

Edited April 1, 2012 by Spyman

[michel123456]

What happened with:

 

 

This last diagram have the companion comoving in the present and not at the surface of the Past Light Cone.

If you transform this dynamic diagram into a regular static space-time diagram, you will obtain the standard light cone described by the trajectory of the yellow dot. The black dot was observable at the intersection with the diagonal when the yellow dot reached it, and it is on the diagonal that the black dot is placed on a space-time diagram.

Edited April 1, 2012 by michel123456

[Spyman]

If you transform this dynamic diagram into a regular static space-time diagram, you will obtain the standard light cone described by the trajectory of the yellow dot. The black dot was observable at the intersection with the diagonal when the yellow dot reached it, and it is on the diagonal that the black dot is placed on a space-time diagram.

But if you claim that there can only be one, you have to choose where that one is located in time, it can not both be comoving in the present and comoving in different pasts simultaneously, that is a large contradiction.

[michel123456]

But if you claim that there can only be one, you have to choose where that one is located in time, it can not both be comoving in the present and comoving in different pasts simultaneously, that is a large contradiction.

Where do you encounter such a situation?

[Spyman]

Where do you encounter such a situation?

With your diagram in post #167 and your statement in post #125.

[michel123456]

With your diagram in post #167 and your statement in post #125.

I don't understand your objection.

The yellow dot is the information carrier. When it reaches the red dot, the observer at this coordinate observes the black dot at the coordinates on the diagonal.

For him the black dot is physically on the surface of his PLC because nothing can go faster than the yellow dot. The comoving objects in present time are not part of the physically observable reality.

[Spyman]

I don't understand your objection.

The yellow dot is the information carrier. When it reaches the red dot, the observer at this coordinate observes the black dot at the coordinates on the diagonal.

For him the black dot is physically on the surface of his PLC because nothing can go faster than the yellow dot. The comoving objects in present time are not part of the physically observable reality.

But you claim that there is only ONE comoving object and that this object is located at the past light cone for the observer.

 

That is certainly not compatible with the notion of another duplicate of this same object comoving in the observer's present.

[michel123456]

But you claim that there is only ONE comoving object and that this object is located at the past light cone for the observer.

 

That is certainly not compatible with the notion of another duplicate of this same object comoving in the observer's present.

???? there is no duplicate.